The world of polymers has progressed rapidly to transform material science from wood and metals of the 19th Century to the use of thermoset polymers of the mid-20th Century to the use of thermoplastic polymers of later 20th Century.
Thermoplastic elastomers (TPEs) combine the benefits of elastomeric properties of thermoset polymers, such as vulcanized rubber, with the processing properties of thermoplastic polymers.
Thermoplastic elastomers presently are prepared from fossil-fuel derived polymer resins, such as styrene block copolymers (SBCs), thermoplastic vulcanizates (TPV), thermoplastic olefins (TPO), copolyesters (COPE), thermoplastic urethanes (TPU), copolyamide (COPA), and most recently olefin block copolymers (OBCs).
Recently thermoplastic elastomers have included polyphenylene ether (PPE). Two examples are found in U.S. Pat. No. 6,838,503 (Yin et al.) and U.S Pat. No. 7,005,465 (Sato). But the formulations disclosed in these two patents apparently do not have sufficient elongation to satisfy Underwriters' Laboratory Test 62 (UL 62), which requires, among other things, more than 200% tensile elongation before aging and retention of more than 75% of that tensile elongation after aging at 121° C. for 168 hours or preferably at 136° C. for 168 hours.
More recently, an excellent thermoplastic elastomer compound has been disclosed in United States Patent Application Publication No. 20120037396 (Gu), which is incorporated by reference herein. The flame-retardant thermoplastic elastomer compound so disclosed has polyphenylene ether, a hydrogenated styrene block copolymer, at least one solid non-halogenated phosphorus containing flame retardant, and a nucleated olefinic polymer. The TPE compound has a before-aging tensile elongation of >200% and an after-aging tensile elongation residual of at least 75%, according to the UL 62 test, which makes it useful as an insulation layer, a jacketing layer, or both for protected electrical lines such as alternating current wire and cable products, accessory cables, and variety of injection molded electrical or electronic parts. The TPE compound was suitable for interior uses.